At a synapse, the gap between two neurones is about 20 nm20\ \text{nm}20 nm wide.
Give 20 nm20\ \text{nm}20 nm in metres. Give your answer in standard form.
Botulinum toxin is a poison made by bacteria. It stops the release of neurotransmitter from motor neurones at the synapses with muscles.
Explain why botulinum toxin causes paralysis.
Doctors inject very small amounts of botulinum toxin into some muscles that contract too often.
Suggest one risk of this treatment.
An impulse travels more slowly across a synapse than along an axon.
Explain why.
43 exam-style questions on Edexcel GCSE Biology 2.3 The nervous system and brain, covering 2.3.1 Structures and functions of the brain, 2.3.2 Imaging brain function with scanning, 2.3.3 Limitations in treating nervous system damage, 2.3.4 Neurones and impulse transmission, and 2.3.5 Structure and function of a reflex arc. Each one has a worked solution and a mark scheme showing where the marks go.